Usually, a channel is created by just joining it. However, if you want it to remain created even if no one is in the channel or if you want to always be in control of the channel (op, admin, founder, etc), then you need to register the channel. That is only possible on networks that have channel services that include channel registration. Not all networks allow registering channels, so you need to keep people ops in the channel at all times to maintain control of the channel.